The present invention is directed to a system and method for preventing the transmission of the family of Human T-Lymphotropic Retroviruses/Viruses (HTLV), in particular type-III, to individuals receiving blood by transfusion. The present invention is especially directed to maintaining a closed (steriIe) sYstem and technique for collecting and transfusing blood components while neutralizing any Human T-Lymphotropic Retroviruses present without impairing the integrity of the system.
Recently, with the increased incidence of the deadly Acquired Immunodeficiency Syndrome (AIDS) and its causative agent, Human T-Lymphotropic Virus type-III (HTLV-III)/Lymphadenopathy-associated Virus (LAV) occurring in the general population, more and more cases of AIDS-related transfusion have been reported, (Peterman et al. JAMA, Vol. 254, No. 20, pp. 2913-2917 Nov. 22-29, 1985).
AIDS has infected over 17,000 Americans. The syndrome, caused by a virus known as HTLV-III or LAV, is spread primarily through sexual contact, sharing of hypodermic needles and transfusion. The groups at highest risk for AIDS in this country are male homosexuals and intravenous drug abusers However, a small number of cases have been caused by blood transfusion and the use of blood products such as plasma, platelets, red blood cells and coagulation factors such as Factor VIII, used by hemophiliacs. Concern for the safety of the blood supply has led the Federal Government to encourage development of a test to screen blood for antibodies to the HTLV-III/LAV virus.
The first generation of such tests, known as Enzyme-Linked Immunosorbent Assay (ELISA) tests, have recently been licensed for use in screening blood donations. These tests however, detect only antibodies for the virus and are less sensitive than screening tests that can detect the virus.
It is difficult to estimate how many AIDS cases will be avoided by screening blood. Additional complications are introduced when we consider that an individual infected with HTLV-III by a blood transfusion may, in turn, infect others, primarily sexual partners who may in turn infect still others. Thus each infection due directly to transfusion may result in numerous instances of secondary infections linked to a single transfusion event.
How frequently will a false negative test occur (Pearl et al. The Public Policy Implication of HTLV-III Antibody Screening in the Commonwealth of Massachusetts, Massachusetts Department of Health, 6/18/85 revision):
First, tests of blood from a group of individuals who although seropositive, are not detected by ELISA tests.
Second, tests, of blood from a small group of individuals who, although truly antibody negative, are virus positive. These people, although true ELISA negatives in the sense that no antibodies are present, are in a more significant sense "false negatives" since they carry HTLV-III virus.
One published study suggests that perhaps 4% of virus positive individuals are not antibody positive (Salahuddin S. Groopman J, et al. HTLV-III in Symptom-Free Seronegative persons. Lancet 1984; December 22/29: pp 1418-1420). Further preliminary work, suggests that the figure may be between 5% and 10%.
According to recent studies, it is estimated that between one to two million people are seropositive in the United States for HTLV-III virus and are most probably carriers that can transmit the virus. Because of the increased prevalence of the HTLV-III virus in the general population and its long incubation period (up to 7 years) (Peterman et al. JAMA Vol 254, No. 20 pp. 2913-2917 Nov. 22-29, 1985). AIDS-related transfusions are likely to be implicated in more and more cases. The above mentioned data reveal that current tests used to screen blood donors may reduce AIDS-related transfusions but are far from eliminating them.
Researchers at the Centers for Disease Control reported that the "The epidemiologic pattern of transmission of AIDS is strikingly analogous to that of Hepatitis B, e.g. from person to person, through sexual contact and through exposure to blood and its products" (D. Peter Drotman, JAMA, August 23-30, 1985-Vol 254, No. 8, Questions and Answers, page 1085). According to the Technical Manual of the American Association of Blood Banks, Ninth edition, 1985 page 349: "Transfusion-associated Hepatitis B decreased since blood banks switched to predominately volunteer blood and adopted mandatory Hepatitis B surface antigen (HBsAg) screening of all donors. However, despite the most sensitive tests for HBsAg detection, occasional cases of Hepatitis B continue to occur after transfusion". Clearly, more effective techniques than screening tests are needed to avoid the spread of life-threatening pathogens such as HTLV-III through transfused blood.
According to current transfusion practice, blood is collected as whole blood containing all the blood components: Plasma, Packed Red Cells, Platelets, White Cells (Leukocytes) and coagulation factors. Using different centrifugation protocols, the whole blood can then be divided into its components.
Often, at least two blood components are transfused to different patients from a single blood unit. Whole blood contains in general 40% packed red cells and 60% plasma. Once the packed red cells are separated, the blood becomes very thick and is usually diluted before transfusion.
According to the Food and Drug Administration (FDA) regulations, once the whole blood unit is collected, it is considered a closed (sterile) system and can be stored for up to seven weeks depending on the anticoagulant and preservative used. The whole blood can be manipulated within the different bags of the original unit but no additional bag can be added. Once an additional bag is connected or a sample taken from the main blood bag, the system is considered opened and the blood has to be transfused within 24 hours or be discarded.
The present invention is therefore concerned in having a permanently attached satellite container to the original blood collection unit containing an appropriate agent for neutralizing pathogens, in particular HTLV-III, in the collected blood without destroying the integrity of the closed (sterile) system.